Normal modes of a Si(100) double-paddle oscillator

Six low-frequency eigenmodes of a double-paddle oscillator have been measured and have been identified with a finite-element model. The internal friction Q−1 of these modes has been measured in the range of 4–80 K. Only one of the oscillator’s modes has a Q−1<3×10−8 below 40 K, which is furthermore very reproducible. All other modes have a higher internal friction which is not as reproducible and also sometimes changes after thermal cycling. It is shown that the internal friction of the different modes is related to the restoring force needed to hold the oscillator in place. The finite-element model is used to predict the damping of the different modes.